Carbon capture and storage (CCUS) involves extracting CO2 from large point sources like fossil fuel power plants or industrial facilities and injecting it permanently into deep geological formations like depleted oil and gas reservoirs or saline aquifers.
Captured carbon dioxide must first be refined using a liquid solvent such as amine to achieve near-pure purity before being compressed for transport.
Capture
Carbon Capture and Storage (CCS) technology is one tool that can assist industries that are slow to decarbonise, such as coal power plants. CCS works by collecting carbon dioxide before it enters the atmosphere at industrial facilities and power plants before transporting and storing it safely within geologic formations.
At present, 15 carbon capture and storage (CCS) facilities are operational in the US, while another 121 projects are underway or planned – these combined have the potential to capture approximately 0.4 percent of current US emissions.
This capacity falls far short of what’s necessary to limit global warming to 1.5 degrees Celsius or lower – as outlined by climate scenarios from the Intergovernmental Panel on Climate Change (IPCC). Other technologies like bioenergy with carbon capture and storage (BECCS) or direct air capture offer similar potential but should be combined with wider action on carbon mitigation.
Compression
Carbon dioxide emissions are collected from power plants that burn fossil fuel or industrial processes such as the production of cement and steel. Once collected, CO2 is compressed and transferred by pipelines, ships or rail tankers to underground storage sites via pipelines, ships or rail tankers – usually depleted oil and gas reservoirs or saline aquifers are preferred – in order to permanently store its climate-changing gases out of the atmosphere where further climate change would result.
CCS begins by cleaning the flue gases produced by power plants before being compressed, which is accomplished using an amine scrubbing process. Flue gas from power plants is piped to large vessels filled with an amine solvent and scrubbed using high temperature steam until near pure air emerges.
Some carbon capture technologies don’t rely on an amine-based system for successful implementation, including pre-combustion CCS in which fuel is gasified before being burned in a combined-cycle power plant, creating carbon dioxide and hydrogen mixtures which are then captured for long-term storage purposes while the hydrogen can drive conventional turbines for driving purposes.
Transport
Once captured, CO2 must be transported to its storage or utilization sites for storage or use. Pipelines provide efficient long-distance transport while trucks or ships can transport smaller volumes over shorter distances.
Carbon transportation operators have recently emerged in key industrial regions to facilitate emissions. Prior to transport, CO2 is compressed or liquefied into its supercritical state for easier handling – making it 50-88% denser than water with 100 times lower viscosity.
Once fabricated, it is then carefully placed into deep geological formations such as depleted oil and gas fields or underwater saline aquifers to ensure safety and long term security. These locations are carefully chosen and monitored to ensure maximum protection.
Once a storage site has been selected, structural trapping ensures that carbon stays underground without migrating laterally or vertically. This is achieved by injecting CO2 under an impermeable barrier like “cap rock,” which acts as an impassible barrier preventing it from leaving its formation and entering other spaces.
Storage
Carbon capture and storage technology has the potential to dramatically cut emissions from industries that are difficult to decarbonize such as manufacturing and power generation, while also mitigating emissions from fossil fuel energy sources like coal or gas plants by capturing and storing their greenhouse gases.
Captured CO2 gas is compressed into liquid-like form before being transported by pipeline or ship to a storage site, either for permanent injection into geological formations such as used oil and gas reservoirs or deep saline formations for long-term storage.
CCUS technology is an essential part of combatting climate change, and policies like the European Union’s Net Zero Industry Act, 45Q tax credit in the US, and Denmark’s CCUS Fund have helped raise global attention and investment in this technology. However, many community groups and environmental advocates remain wary that CCUS could have negative repercussions for polluting facilities by serving as a “band-aid” to emissions intensive industries that harm vulnerable communities.